page_title: Medusozoa
section_title: Characteristics
hierarchical_section_title: Medusozoa / Characteristics
caption_attribution_description: Italiano: Pelagia noctiluca
context_page_description: Medusozoa is a clade in the phylum Cnidaria, and is often considered a subphylum. It includes the classes Hydrozoa, Scyphozoa, Staurozoa and Cubozoa, and possibly the parasitic Polypodiozoa. Medusozoans are distinguished by having a medusa stage in their often complex life cycle, a medusa typically being an umbrella-shaped body with stinging tentacles around the edge. With the exception of some Hydrozoa, all are called jellyfish in their free-swimming medusa phase.
context_section_description: Medusozoans differ from anthozoans in having a medusa stage in their life cycle. The basic pattern is medusa (usually the adult or sexual phase), planula larva, polyp, medusa. Symmetry is tetramerous, with parts in fours or multiples of four. The mitochondrial DNA molecules are linear rather than circular as in anthozoans and almost all other animals. The cnidae, the explosive cells characteristic of the Cnidaria and used in prey capture and defence, are of a single type, there being nematocysts but no spirocysts or ptychocysts. In contrast, the anthozoan life cycle involves a planula larva which settles and becomes a sessile polyp, which is the adult or sexual phase.
caption: Pelagia noctiluca, a scyphozoan
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